As electronic circuits become denser, faster and more complex, it is increasingly important to remove the heat generated by circuit components before the heat deteriorates component or circuit performance. Such heat removal is particularly difficult from a substrate surface populated by circuit components because the components are of varying height, varying heat generation, and varying thermal conductivity.
Conventional methods of removing heat from populated surfaces are less than satisfactory. One approach, commonly used with printed wiring boards, involves filling the space between the surface and an overlying thermal plane (metallic heat sink) with thermally conducting organic material. The material is commonly applied as a soft, conforming "thermal grease" and sometimes as a loaded sponge. Unfortunately organic materials are of limited assistance. Although better than air, the thermal conductivity of even well loaded organics is orders of magnitude less than highly conductive materials such as copper. Organic loading gives rise to fairly high thermal resistance in spite of high contact area.
A second approach is the use of contoured heat sinks or contoured intermediate plates. Aluminum or copper plates are specifically contoured to touch the PWB surface at critical areas. While this approach is thermally superior to organic loading, it is expensive and inflexible in that each different PWB design requires a redesigned contour. It is difficult to apply contoured plates by mechanized assembly. Accordingly there is a need for an improved connection arrangement for removing heat from component-populated substrate surfaces.